First of all: I am not into golden shower or similar stuff. But I know, that many women consider peeing something very intimate ...

It is a hot summer. Brad and Laura are siblings. They visited someone. Since it is so hot, they both drank a lot.
Some time later, they leave. They drive home in the car, when Laura tells her brother to stop at the side of road, in a secluded parking lot, because she really needs to pee. She can't wait until they are at home.

They both get out of the car (Brad wants to smoke a cigarette). Laura goes behind some bushes and raises her skirt. Then she pulls her panties aside (or maybe she doesn't wear any). Then she starts to pee. Suddenly, she looks up and realizes that her brother is watching her pee - but she can't stop.
"Hey, don't look." She can't cover her pussy with her hand, since she is still peeing,
"Oh, come on Sis, there is nothing special about it. See, I have to pee, too." He opens his pants and pulls his dick out.
So sister keeps on peeing, while brother stands near her, with his dick in his hand.
"So at least stop staring at my pussy ..."
"Why? You are also looking at my dick ... and don't tell me, you don't like what you see ..."
"Yeah, and I am sure, you love to see my pussy ... since your dick is getting harder and harder ..."
"Well sister, you know, a dick and a pussy are not just for peeing ..."
"Wait, do you try to suggest we should fuck right now?"
"Yes, why not. You know, taboo sex is the hottest sex."

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"We have done so much, with so little, for so long, that now we can do almost anything with nothing." - Dave Marcis